Convert mp3s for podcasts into mp3s that will show up in iOS Music (not Podcasts) app

I would like to convert mp3 files for podcasts into "plain" mp3 files of the kind that when synced to iOS will show up in the Music app's playlists but not in the Podcasts app.

I've had some success in the past with converting ID3 tags to version 1.0 (Convert ID3 Tags ... in context menu) but for some reason this does not seem to work with current iTunes 12.

So how can one perform this conversion on OS X Yosemite (with iTunes 12), preferably without third-party software?